4. Operation ......................................................................................................................... 29
4.1 Synchronization between tap-changer and motor-drive mechanism .......................... 29
5. Inspection ......................................................................................................................... 30
5.1 General ..................................................................................................................... 30
5.2 Inspection ................................................................................................................. 30
5.3 Checking oil quality ................................................................................................... 31
5.4 Maintenance ............................................................................................................. 31
5.5 Replacement of the complete switching mechanism including vacuum interrupters .. 31
6. Troubleshooting ................................................................................................................ 32
7. Repairs and adjustments .................................................................................................. 33
7.1 General ..................................................................................................................... 33
8.1.1 Serial number ..................................................................................................... 33
7.2 Oil leakage ................................................................................................................ 33
7.2.1 General .............................................................................................................. 33
7.2.2 Tools required ..................................................................................................... 33
7.2.3 Materials and spare parts required ...................................................................... 33
7.2.4 Procedure .......................................................................................................... 33
7.3 Replacement of pressure relay .................................................................................. 35
8. Electrical diagrams ........................................................................................................... 36
8.1 Standard circuit diagram BUE ................................................................................... 37
8.2 Contact timing diagram BUE ..................................................................................... 38
8.3 Standard circuit diagram BUL2 ................................................................................. 39
8.4 Contact timing diagram BUL2 ................................................................................... 40
9. Technical data .................................................................................................................. 41
9.1 Dimensions ............................................................................................................... 41
9.2 Weights .................................................................................................................... 41
9.3 Specification of materials
.......................................................................................... 41
9.3.1 General .............................................................................................................. 41
9.3.2 Tap-changer housing .......................................................................................... 41
9.3.3 Selector switch ................................................................................................... 41
9.3.4 Gearing mechanism ........................................................................................... 42
9.3.5 Drive shaft system .............................................................................................. 42
